JPS5956585A - Treatment of used acid pickled paste - Google Patents

Abstract

A process for treating spent fluoride-containing pickling paste on metal surfaces by applying to the spent pickling paste on the metal surface an aqueous treating paste composition comprising calcium carbonate having a particle size not in excess of about 5 microns and an alkali metal bicarbonate, which composition has a pH which is not in excess of about 9.5.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a method for converting the fluoride-containing pickling paste of spent filters present on metal surfaces into products that do not pollute the environment.

For example, from the surface of metals made of steel and/or aluminum and their alloys, worthless and corrosion-promoting effects, such as those produced during heat treatment (J31) or by the effects of the outside world, can be removed. It is common practice to remove certain oxides JT't.

This removal treatment is carried out exclusively with acid solutions based on, for example, hydrochloric acid, sulfuric acid, phosphoric acid or fluorinated water (phosphoric acid).

Particularly if the product is large or if oxides are formed locally, it is also possible to apply a powder-containing paste to the area to be cleaned. By doing so, the oxide part and this attached 11)
As the material is dissolved, the oxide loses its adhesion to the fully curved surface. Such material may be washed away with water or removed using a push-pull after a suitable period of time.

This kind of pickling paste based on phosphoric acid or f,
The de-q paste contains saponifiable oils, for example as thickeners, or vinyl fatty acids which are converted into soaps (
German Patent Application Plagiarism No. 1082475 #IIl
'i'F).

Other purifying or etching agents that have already been published include fluorinated hydroacids, magnesium compounds, and at least one free acid from the group consisting of nitric acid, phosphoric acid and sulfuric acid or its derivatives, and certain sulfones. It is regretted from acid (
Germany'l? Patent Application Publication No. 195 (No. 1560 No. 4...
book).

Finally, it contains, in addition to fluoride ions, a mixture of calcium compounds and iron and/or aluminum compounds, with at least 10 free ri? (1
Pickling pastes and rust removal pastes have been proposed that have an acidity equivalent to (calculated as 00% TIF);
Pickling pastes of this type are used in particular for treating steel alloys.

When using a pickling paste containing heptadide, r7? Unlike the use of canal fluid, special problems arise. This means, on the one hand, that the normally used cleaning tanks cannot be used, and on the other hand, the strongly acidic fluoride-containing waste water produced when washing away the used pickling paste cannot be used for other post-treatments. This means that they must not be released or otherwise discarded without treatment.

It is common practice to treat this type of wastewater and bring it to a pH value of 6.5 to 95 by adding calcium hydroxide, whenever possible. . The insoluble calcium fluoride formed during the reaction is liberated by precipitation and only a clear liquid is discharged.

However, another problem that arises in this case is the n! ? The il'3 solution often undergoes after-reactions, so that when calcium hydroxide is used in excess, the %1) II value rises again beyond the permissible limits.

Therefore, when treating such wastewater, it is necessary to accurately measure its alkalinity and to carry out adjustment operations that are often time-consuming and involve various checks.

Another proposal for flowing acidic wastewater containing fluoride over granulated calcium carbonate, e.g.
This alone is not very effective, simply because it will be coated with chlorine and therefore further reactions will be stopped.

The object of the present invention is to eliminate the various drawbacks of known methods, and to convert spent pickling waste present on the surface of the metal in a simple and inexpensive manner. The goal is to provide the following.

The above-mentioned subject is solved according to the invention [in a method of the type mentioned at the outset, up to 50% of the used pickling paste is
This is achieved by applying an aqueous paste containing calcyanocarbonate with a particle size of μrn and an alkali bicarbonate and having a pH value of 25 mcg.

The amount of calcium ions supplied must be so high that the fluoride ions contained in the used pickling paste are converted by the calcium into insoluble calcium fluoride. A neutralizing effect is carried out by the coagulation with the simultaneous presence of alkali hydrogen carbonate, so that the pH value of the aqueous solution, even in the case of excess use, is 8.4 (1% hydrogen carbonate) as an IJium solution. It won't be any higher than that (measured).

It should be noted that for the necessary 1 hour, an alkaline compound such as I
By adding a small amount of Qnl Natriuno, p
H value up to 9.5).

The size of particles in calcium carbonate, that is, the particle size, is important when it is 5μ? This is because particles larger than 11 no longer react completely. Due to the formation of the outer layer of calcium fluoride, the internal calcyanocarbonate no longer reacts with fluoride ions or acids. As the particle size of the calcium carbonate decreases, the conversion is more complete, the reaction rate is increased, and the ease of applying the paste is improved.

For this purpose, according to a preferred embodiment of the present invention, the diameter of the calcium carbonate component is 27 tm or less, preferably 4 J
The method is to apply a paste with a thickness of 1 μm or less.

This 1. , r5, the use of precipitated calcium carbonate is particularly preferred.

Further, according to another embodiment suitable for the bamboo of the present invention, 20 to 50% by weight, preferably 30 to 4% by weight of calcyano carbonate is added.
Contains 0 weight j7t%, and uses alkaline hydrogen carbonate I basin as N8.11CO3, total n: L, te, 2tJ~
50 fold Fa [, preferably 5 [J □-” 4 [
1 fold 'rJ, % fil.

The paste containing in ' is applied onto the used pickling paste.

Furthermore, another preferred implementation of the process according to the invention ('4 Ql. 11.1-10 f/k/ky paste
When applying a paste containing a surfactant, preferably having an O9 to low level, the spreadability of the paste is as good as 1 yen, and the reaction progresses satisfactorily (D'-). Particularly suitable surfactants for use in this CQ combination are nonionic or anionic surfactants, especially ethoxylated alkylphenols.

Current bets on wastewater quality j, p according to l1 law
It may be more preferable to use a paste with an II value of 8 to 9 as 51H and cloth 4.

Usually this type of paste is applied with a brush. Has the viscosity of the paste been adjusted to a low level? ), spraying can also be applied by method. The Ll of the paste to be applied in each case must be at least the same as the mouth of the applied pickling paste. Even if the situation reaches 6, there will be no delay at all when it comes to environmental pollution.

The conversion of the used i'7-washing paste into an environmentally compatible, non-polluting product results in the evolution of carbon dioxide gas, and the end of the evolution of this gas simultaneously indicates the end of the reaction.

Therefore, for example, p I (I) is not necessary to monitor the course of the reaction by measuring the value. The time required for conversion is generally 1 to 5
Within minutes.

After the reaction is complete, the conversion products present on the gold FS surface are
Most young cattle are removed by water. This removal operation can be carried out with a brush or by a spraying operation, depending on the nature of the metal surface treated. The washing liquid in this case is filtered or degucted to remove insoluble components as far as possible and the aqueous phase is discharged into the drainage system.

The most outstanding advantage of the method according to the invention is that the i
p! il W'! ! Further important advantages include the low cost of the chemicals required, the long shelf life of the paste, and the fact that no special care is required for handling the paste. However, there is no problem with the amount of paste used; in particular, if it is used for publication, special measures may need to be taken depending on the case. Finally, can the obtained conversion product be used in cosmetics without any special measures? /) can discharge the existing J-1+' water phase (iifi lt' water phase) if necessary.

Next, the method of the present invention will be described with reference to an example: This experiment was carried out on a weighted tube shape made of chromium nickel steel with a welded seam. A pickling paste was applied with ゛.The composition of this pickling paste is as follows: Nitric acid (#50% by weight) 60 heavy R-hydrogen thifluoride P (concentration 40 heavy F1) 15 heavy thiosulfuric acid The action time of this paste was set to 15 minutes. Comparative Example 1 To perform a comparison, calcium carbonate ground to a particle size of 10 to 15 μm was mixed with a solid content of 40% barium. It is mixed with water to form a paste with a pH value of 8.5 and applied on the used pickling paste at a rate of 100F per meter of welded seam.After a working time of 5 minutes, the conversion product is After rinsing off, a wash solution was obtained with a pH value of 4.0 and a fluoride ion content of 180 my/l, which could not be discharged without modifying the pH value.

It should be noted that even if the amount of paste applied on the pickling paste was doubled, and therefore the amount of calcium supplied was significantly increased, no significant difference was observed in the results, and the resulting cleaning solution had a pH value of 5.0. The fluoride content was 140 mg/l, and this cleaning solution could not be disposed of or discharged as it was.

Comparative Example 2 In order to carry out yet another comparison, precipitated calcium carbonate having a particle size of approximately 1 μm was prepared with a solid content of 40% by weight, p.
A paste with an II value of 8.5 was prepared and applied onto the used pickling paste with air at 100F per meter of weld seam.

After an action time of 5 minutes, the conversion products were washed away and the pH value was 5.4 and the fluoride content was 70 my/min.
1 of washing liquid was obtained. This cleaning solution also has a high pH
It was not possible to emit it without modifying the value.

Example 1 The composition of a paste made in N'W for carrying out the method of the invention is as follows: Calcium carbonate (particle size 1 μus) 35% sodium bicarbonate 35% sodium bicarbonate 2. town water
The remainder of this paste was also applied in an amount of 100 f per bolt weld seam lnt onto the used pickling paste and washed off after an action time of 5 minutes.

The p II value of the cleaning solution obtained in this case is Z2,
The fluoride content was 20 m (p/l).
It was possible to release to 1 ifi.

The application month of the example paste was doubled and the weld seam was 1 nS less than 20
Example 6 was repeated except that 0y- was used.

Despite the fact that the paste at t3 according to the present invention has a considerable excess of 11%, the pIT value of the obtained cleaning solution is Z8, which is only 10%, and the fluoride content is 16m6>/
e, and as in the case of this cleaning liquid ζJ Example 5, it could be directly discharged into the drainage facility lj:i.

The invention can be summarized as follows.

In a method for converting used fluoride-containing pickling paste present in Gold Pi %'< surface 2 into a product that does not pollute the environment, calcium carbonate and alkali carbonate are used. An aqueous paste containing hydrogen salts and having a pJI value of up to 95 is applied. The maximum allowable particle size of calcium carbonate is 51t nt, preferably less than 2t+m, preferably 1μl
It is less than or equal to Fi.

This paste is calcylano-2[1-5['l
It is preferable to contain 20 to 50 m of alkali hydrogen carbonate, and if necessary, a base activator of 1 ky O, 1-101.

Agent Katsu Ueya Shun Sugiura rt

Claims (1)

[Claims] 1. A method for converting a used fluoride-containing pickling paste present on a Kanakura surface into an environmentally compatible product, wherein the used pickling paste contains up to 5μ
? ? A method characterized in that an aqueous paste containing carbonate carboxylates and alkali bicarbonates having a particle size of 1.1 and a pJ value of up to 95 is applied. 2. The method according to claim 1, characterized in that a paste is applied in which the calcilano carbonate component has a particle size of less than 2 μm, preferably less than 11 tnt. It is recommended to apply a paste containing calcium carbonate in an amount of 20 to 50 t%, preferably 30 to 40 t%. The method according to claim 1 or 2, characterized in that 4. 4+! characterized in that a paste containing an alkali hydrogen carbonate in an amount of 20 to 50% by weight, preferably 50 to 40% by weight calculated as NaHCo 5 is applied! ? A method according to any one of claims 1 to 3. 5. Claims 1 to 4 characterized in that a paste containing 0.1 to ioy'', preferably 0.5 to ioy'' of surfactant per 1 kg of paste is applied. 6. The method according to any one of claims 1 to 5, characterized in that a paste having a plI value of 8 to 9 is applied. 71' The method according to any one of claims 1 to 6, characterized in that after the completion of the Z conversion, C is removed from the product by the action of water.